GENEVA (AP) — Here’s what it took to produce Saturday’s U.S.-Russian deal on Syria’s chemical weapons: three days of intense, tough, round-the-clock negotiating spurred by an abrupt U.S. policy change based on a surprise Russian proposal, according to American officials involved in the talks.

Just on Tuesday, President Barack Obama had decided to delay consideration of unilateral military strikes against Syria and explore the Russian idea about securing and destroying the Assad government’s chemical weapons.

That gave U.S. and Russian officials only 24 hours to organize and prepare for the meetings at the same luxury hotel in Geneva where the much-maligned “reset” in relations between Washington and Moscow was inaugurated to great fanfare in 2009.

The 29-member American delegation, led by Secretary of State John Kerry, arrived at the Intercontinental Hotel Geneve at midday Thursday after a turbulent, eight-hour overnight flight from Washington.

The U.S. side had no guarantee that the Russians were interested in an enforceable deal or willing to conclude one quickly, the American officials told reporters. The officials spoke on condition of anonymity because they were not authorized to publicly discuss the negotiations.

Gauging the Russian’ seriousness was a major part of the mission that Obama sent Kerry on. It came only two days after Kerry had opened the door to a potential agreement with an apparently off-the-cuff remark in London that Russian Foreign Minister Sergey Lavrov seized on.

U.S. and Russian teams had met for a year to discuss the eventual disposition of Syria’s chemical weapons arsenal. But those talks had focused on how to deal with the weapons only after Syrian President Bashar Assad’s government had been replaced by a transitional government in a political process, the officials said.

Taking an inventory, isolating the stocks and then destroying them in the midst of a civil war had not been contemplated, they said.

Early in the week, Russia’s ambassador to the United Nations, Sergey Kislyak, had presented U.S. Undersecretary of State Wendy Sherman, the second-ranking U.S. official in Kerry’s party, with two pages of general ideas, the officials said.

“They were useful ideas and we had useful ideas, but no one had a full-blown plan, no one,” one official said. “We had already had some experience working together and sharing expert information, but we did not come to this meeting with a full-fledged plan. The meeting was put together logistically in 24 hours, so people had to create all of this here.”

Within minutes of their first meeting Thursday night, Kerry and Lavrov appeared at odds.

In a joint appearance before reporters, Lavrov made brief, general remarks and then took exception to a lengthy statement that Kerry made. Kerry repeated the U.S. criteria for a deal and the U.S. position that only Obama’s threat of military action had led to the Russian proposal and Syria’s quick decision to accept it and become a party to the treaty that seeks to ban chemical weapons.

Lavrov icily complained that he had not come prepared with an “extensive political statement” and was not going to “lay out here our diplomatic position.”

“The diplomacy likes silence,” he said sternly, before stressing that both sides needed to compromise for the talks to succeed.

When Kerry asked the translator to repeat part of the remarks, Lavrov cut him short.

“It was OK, John,” Lavrov said. “Don’t worry.”

“You want me to take your word for it?” Kerry replied. “It’s a little early for that.”

While humorous and met with laughter, the exchange underscored the difficulties facing the experts tasked with the nitty-gritty negotiations on technical issues.

U.S. officials described the negotiations with the Russians as hard-fought, serious and professional. But, they said, they were not convinced that the Russians were truly serious until they got further into their talks.

“It took a while to make sure we were going to get to something that would be meaningful, verifiable (and) enforceable,” one official said.